public class demo27 {
    //环形链表
/*    public class Solution {
        public boolean hasCycle(ListNode head) {
            if(head == null||head.next == null) return false;
            ListNode s = head;
            ListNode f = head;
            while(f !=null && f.next!= null)
            {
                f = f.next.next;
                s = s.next;
                if(s == f) {
                    return true;
                }
            }
            return false;
        }
    }*/
}
